Intracranial stent and method of use

ABSTRACT

A stent and stent catheter for intra-cranial use. The stent is a rolled sheet stent and is releasably mounted on the distal tip of the catheter by means of a non-sliding retention and release mechanism. The non-sliding release mechanism is operated remotely at the proximal end of the catheter by means of a linear translator. The stent is rolled tightly on the distal tip of the catheter and flexibility of the tightly rolled stent is promoted by ribbed or slatted construction (or, alternatively, slotted construction) in which the various layers of the stent are provided with numerous slats which counter align when the stent is expanded to form an imperforate wall from a plurality of perforate layers.

This application is a continuation of U.S. patent application Ser. No.09/897,218, filed Jul. 2, 2001, now U.S. Pat. No. 6,669,719, which is acontinuation application of U.S. patent application Ser. No. 08/762,110,filed Dec. 9, 1996, now U.S. Pat. No. 6,254,628.

FIELD OF THE INVENTIONS

This invention relates to disease delivery systems for stents to be usedto treat vascular disease.

BACKGROUND OF THE INVENTIONS

The inventions described below were developed with the goal of providingnew and better therapies for certain types of vascular disease for whichthe present day therapies are widely regarded as inadequate. Vasculardisease includes aneurysms which can rupture and cause hemorrhage,atherosclerosis which can cause the occlusion of the blood vessels,vascular malformation and tumors. Occlusion of the coronary arteries,for example, is a common cause of heart attack. Vessel occlusion orrupture of an aneurysm within the brain are causes of stroke. Tumors fedby intra-cranial arteries can grow within the brain to the point wherethey cause a mass effect. The mass and size of the tumor can cause astroke or the symptoms of stroke, requiring surgery for removal of thetumor or other remedial intervention.

Other therapies for occlusions of various arteries are underdevelopment. Balloon angioplasty is a technique in which a balloon isinserted into a stenosis which occludes or partially occludes an arteryand is inflated in order to open the artery. Atherectomy is a techniquein which occlusive atheromas are cut from the inner surface of thearteries. The newly preferred therapy for coronary occlusions isplacement of an expanded metal wire-frame, called a stent, within theoccluded region of the blood vessel to hold it open. Stents of variousconstruction have been proposed, including the Palmaz-Schatz™ balloonexpandable metal stent, the Wallstent self-expanding braided metalstent, the Strecker knitted metal stent, the Instent™ coil stent, theCragg coiled stent and the Gianturco Z stent. Stents have been proposedfor treatment of atherosclerosis in the neck, but carotid endarterectomyis still the preferred treatment for stenosis. Most perioperativestrokes are thought to be caused by technical errors duringendarterectomy (see Becker, Should Metallic Vascular Stents Be Used ToTreat Cerebrovascular Occlusive Disease, 191 Radiology 309 (1994)). Thesame concerns militate against other forms of therapy such asangioplasty for treatment of the carotid arteries. Various factors,including poor long-term patency, distal emboli causing a stroke, thepotential for crushing from external pressure, and the need for longterm anti-coagulation, lead to the avoidance of certain stents invessels smaller than the iliac arteries or in locations susceptible toexternal pressure. See, for example, Hull, The Wallstent in PeripheralVascular Disease, For Iliac Use Only, 6 JVIR 884 (November-December1995).

Stent-grafts have been proposed and used to treat aneurysms in the largeblood vessels such as the aorta, and these typically include tube graftmaterial supported by a metallic stent. These stent-grafts are designedfor use in the large blood vessels, and the various layers of stents andgrafts make them unsuitable for use in smaller blood vessels.Stent-grafts are not currently used in the coronary arteries which aretypically 3 or 4 mm in internal diameter. Rolled stents have beenproposed for use in aortic aneurysms. For example, Lane, Self ExpandingVascular Endoprosthesis for Aneurysms, U.S. Pat. No. 5,405,379 (Apr. 11,1995) suggests the use of a polypropylene sheet placed in the abdominalor thoracic aorta to bridge aneurysms. It is particularly emphasized inLane that the rolled sheet must be imperforate. Winston, StentConstruction of Rolled Configuration, U.S. Pat. No. 5,306,294 (Apr. 26,1994) proposes a rolled sheet of stainless steel. Neither device hasbeen approved for use in humans. The Winston device has not been used inhumans. Of similar construction are the single layer rolled stents suchas Kreamer, Intraluminal Graft, U.S. Pat. No. Re. 4,740,207 (Apr. 26,1988) and its reissue 34,327 (Jul. 27, 1993), which are expanded byballoon and include a ratchet mechanism which projects into the lumen ofthe stent, thus making it unsuitable for critical vessels in the brainand small diameter vessels. Khosravi, Ratcheting Stent, U.S. Pat. No.5,441,155 (Aug. 15, 1995) and Sigwart, Intravascular Stent, U.S. Pat.No. 5,443,500 (Aug. 22, 1995) are other examples of rolled stents withratcheting locking mechanisms.

Aneurysms of peripheral arteries and arteries of the neck have beentreated experimentally with open walled stents such as the Streckerbraided stent. Szikora, et al., Combined use of Stents and Coils totreat Experimental Wide-Necked Carotid Aneurysms, 15 AJNR 1091 (June1994) illustrates use of a Strecker stent in the proximal vertebralarteries in dogs, and teaches that an open walled or porous stent isrequired to avoid excessive ingrowth. The Strecker stent has a smallmetal to blood vessel surface ratio, and has large openings between eachof the wires making up the stent. The current technique in the use ofopen walled stents in the aneurysms of peripheral arteries is based onthe theory that placement of the open walled stent slows the blood flowin the aneurismal sac, leading eventually to the formation of clots andfibrous masses which occlude the aneurysm. This technique has beencombined with placement of micro-coils through the wall of the stent andinto the aneurysm to further encourage fibrous tissue development withinthe aneurysm. The Szikora article and others show that knitted stentshave not been effective in isolating an aneurysm from the circulatorysystem. Another problem noted with this technique is that blood clotscan escape the open walled stent.

Stents have not previously been used for aneurysms of the blood vesselsin the brain. The vessels in the brain likely to develop stenosis,aneurysms, AVM's and side branches requiring occlusion have diameters ofabout 1 mm to 5 mm, and can be accessed only via highly tortuous routesthrough the vascular system. Instead, surgical clipping, resection,complete occlusion with acrylic-based adhesives (super glue) or smallballoons (thereby intentionally occluding the downstream portion of theblood vessel and any portion of the brain supplied by that portion),stuffing with foreign objects, etc. have been used. In a method ofcurrent interest, small coils are stuffed into the aneurysm via acatheter. One such small coil is known as the Guglielmi Detachable Coilor GDC. After placement of a few coils, which partially obstruct bloodflow in the aneurysm, the blood clots or fibrous matter forms within thesac. This technique has reportedly resulted in clots and coils fallingout of the sac, and the technique is not used on wide-neck aneurysms.Aneurysm clipping, in which the skull is opened and the brain dissectedto expose the outside of the aneurysm, followed by placement of clips atthe base of the aneurysm, is also an option for treatment. However,these techniques do not always effect an immediate and complete seal ofthe aneurysm from the high pressure of the circulatory system, andrupture, leakage and deadly complications occur. Aneurysm rupture andbleeding during surgical clipping and shortly after the clip placementis a significant problem and add difficulty to the procedure. Examplesof the problems inherent in the use of both GDC's and aneurysm clips areillustrated in Civit, et al., Aneurysm Clipping After EndovascularTreatment With Coils, 38 Neurosurgery 955 (May 1996) which reports thatseveral patients in the study died after unsuccessful coil placement andbefore they could be re-treated with the open skull clip placement. Thusthe article illustrates that GDC's do not always work, and when theyfail they may leave the patient in a critical condition. As illustratedin the article, bleeding during surgical clipping and shortly after theclip placement is also a frequent problem.

From experiences like this, it is apparent that the ultimate goal ofintracranial aneurysm treatment is the complete or nearly completeexclusion of the aneurysm cavity from the circulation, which preventsbleeding into the brain cavity and prevents formation of distal bloodclots. This goal may be achieved immediately to ensure successfultreatment by means of a substantially imperforate stent. It may also beachieved with a slightly perforated stent which alters flow in such away that compete clotting, over time, is initiated within the aneurysm.It may also be achieved with a perforate stent through which embolicmaterial such as coils are placed in the aneurysm. The treatments may beaccomplished by placement of the stents described below which generallydo not require the use of balloons for expansion of the stent, so thatthe blood vessel being treated is not occluded during placement of thestent.

Typically, the stents described below will be delivered percutaneously,introduced into the body through the femoral artery, steered upwardlythrough the aorta, vena cava, carotid or vertebral artery, and into thevarious blood vessels of the brain. Further insertion into the brainrequires passage through the highly tortuous and small diameterintra-cranial blood vessels. The Circle of Willis, a network of bloodvessels which is central to the intracranial vascular system, ischaracterized by numerous small arteries and bends. Passage of a stentfrom the internal carotid through the Circle of Willis and into theanterior cerebral artery (for example) requires a turn of about 60°through blood vessels of only 1-5 mm in diameter. Clinically, manysignificant aneurysms take place in the Circle of Willis and approachingblood vessels. The stent and delivery systems described herein areintended for use in such highly tortuous vessels, particularly in theCircle of Willis, the vertebral and carotid siphons and other majorblood vessels of the brain. At times, pathologically tortuous vesselsmay be encountered in the deeper vessels of the brain, and these vesselsmay be characterized by small diameter, by branching at angles in excessof 90° and by inaccessibility with guide wires larger than the standard0.018 guide-wires. These pathologically tortuous vessels may also besubject to aneurysms and AVM's which can be treated with the stents anddelivery systems described below.

Various inventors have proposed systems for delivering stents into thelarger less tortuous vasculature of the abdomen, chest, arms and legs.Garza, Prosthesis System and Method, U.S. Pat. No. 4,665,918 (1987),describes a delivery system for a stent designed to open an occlusion ina blood vessel. The stent is rolled on a catheter, and the catheter iscovered with a sheath that fits closely over the catheter. The stent isheld in place on the catheter by the sheath, and is released by pullingthe sheath backward (proximally) to uncover the stent.

Winston, Stent Construction of Rolled Configuration, U.S. Pat. No.5,306,294 (Apr. 26, 1994) shows a rolled sheet stent intended for use inbridging aneurysms and opening occluded blood vessels. The stent is selfexpanding, and does not require a balloon to force it to unwind to adiameter large enough to engage the aorta with enough force to hold itin place. The delivery system shown in Winston includes a rolled stentrolled upon a spool which in turn is mounted on the distal tip of adelivery catheter. The assembly is housed within the lumen in the distaltip of a guide catheter. Control wires shown in Winston may be used tohold the stent in the tightly wound state, and may be pulled proximallyto release the stent.

Lane, Self Expanding Vascular Endoprosthesis for Aneurysms, U.S. Pat.No. 5,405,379 (Apr. 11, 1995) shows a rolled sheet stent intended foruse in bridging abdominal aneurysms. The stent is self expanding, anddoes not require a balloon to force it to unwind to a diameter largeenough to engage the aorta with enough force to hold it in place. Thedelivery system shown in Lane includes a rolled stent inside the lumenin the distal tip of a delivery catheter, and a push rod located behindthe stent. The stent is deployed when the push rod is used to push thestent distally out the end of the delivery catheter as the deliverycatheter is pulled proximally to uncover the stent and allow it tounwind.

Kreamer, Intraluminal Graft, U.S. Pat. No. 4,740,207 (Apr. 26, 1988)shows a tube stent, comprising a solid walled tube with ratchetingtongue and groove mechanism. The stent is mounted on an angioplastyballoon and expanded to size within an artery by force of the balloon.Likewise, Sigwart, Intravascular Stent, U.S. Pat. No. 5,443,500 (Aug.22, 1995) shows a rolled stent, comprising a rolled lattice withratcheting mechanism. The stent mounted on an angioplasty balloon andexpanded into place by force of the balloon. A pull wire threadedthrough the lattice of the rolled stent helps hold the stent in place onthe balloon during delivery through the vasculature. Sigwart does notdiscuss the mechanisms and methods for delivering the stent to thetarget site within the blood vessel.

SUMMARY

Stents for intra-cranial use and methods for using these stents aredescribed in detail below. The physical characteristics of prior artballoon expandable stents and self expanding stents make them clearlyunsuitable for intra-cranial use, because of their delivery profile andtendency to temporarily occlude the vessel during deployment. They havenot been proposed for intra-cranial use. Palmaz stents, Palmaz-Schatz™stents, Wallstents, Cragg stents, Strecker stents and Gianturco stentsand other stents are too rigid to allow placement in the cerebral bloodvessels, some require a balloon for deployment, and all are too open toocclude an aneurysm. Presented below are several embodiments of stentssuitable for intra-cranial use, along with methods for using thesestents to treat intra-cranial vascular disease.

The self expanding rolled sheet stent is suitable for use in theintra-cranial arteries. The rolled sheet is made of Elgiloy™, nitinol,stainless steel, plastic or other suitable material, and is impartedwith resilience to urge outward expansion of the roll to bring therolled stent into contact with the inner wall of a diseased artery. Therolled sheet is adapted for easy insertion and non-deforming radialflexibility to facilitate tracking along the tortuous insertion pathwaysinto the brain. In some embodiments, as much of the material of thestent is removed as is consistent with eventual creation of a solidwalled stent upon unrolling of the stent within the blood vessel. Theunrolled stent may be two or more layers of Elgiloy™, thus providingradial strength for the stent and creating at least a slight compliancemismatch between the stent and the blood vessel, thereby creating a sealbetween the stent and the blood vessel wall. For placement, the stent istightly rolled upon or captured within the distal tip of an insertioncatheter. The release mechanism is extremely low profile, and permitsholding the rolled stent in a tight roll during insertion and permitsatraumatic release when in the proximity of the site of arterialdisease, without occluding the vessel with the deployment catheter. Thestent can be placed in the intra-cranial blood vessels (arteries andveins) of a patient to accomplish immediate and complete isolation of ananeurysm and side branches from the circulatory system. The stent may beplaced across a target site such as an aneurysm neck, origin of afistula, or branch blood vessels feeding a tumor in order to redirectthe flow of blood away from the target. It can be used as a stand alonedevice which is left in the intra-cranial artery permanently, or it maybe used as a temporary device which allows for immediate stabilizationof a patient undergoing rupture of a blood vessel an aneurysm orawaiting open skull surgery for clipping or resection of an aneurysm.The stent can be used for stabilization and isolation of a vasculardefect during surgery of the vascular defect. Another advantage of thistype of stent is that it can be wound down should repositioning berequired prior to full release. It is possible to rewind and repositionor remove the device using grasping tools.

The stent delivery systems described and claimed below incorporate thenecessary structural modifications and features needed to provide thedesired handling characteristics of an intra-cranial stent deliverysystem. For the most part, they are designed with the self expandingstent in mind, but they will prove useful in some applications ofballoon expanding and shape memory stents. The delivery systems permitdeployment of rolled sheet stents made of extremely thin Elgiloy™,nitinol, stainless steel or plastics with less concern over problemsthat may occur during deployment of the stent when deployed with themechanisms disclosed in the prior art.

The delivery systems are comprised of two parts, proximal controlmechanism and distal retaining and release mechanisms. For proximalcontrol mechanisms, a slide operated by threaded knob, jack screw ortrigger pull mechanism is used to provide smooth, powerful pull-back ordistal pushing motion to a translating member. The translating memberconnects the proximal mechanism to the distal release mechanism andtranslates movement of the proximal mechanism into movement of thedistal mechanism. The translating member can be a hypotube, stiff wire,thread, coiled or braided wire catheter or guide-wire, nylon line,micro-tubing, with rigid examples capable of providing both proximal anddistal translation and flexible limp examples being only capable ofdistal translation. The distal retaining mechanisms provide for releaseof the rolled sheet stent with as little additional structure aspossible, and provide for non-sliding release of the stent. The proximalremoval of a sheath is not required, and the distal push of a push-rod,core, or catheter is not required, so that the rolled stent need notslide past the structures used to place the stent. This is accomplishedin various embodiments by using tear-away sheaths which are operatedwith zip cord, a zip-strip construction common to commercial cellophanepackaging, and a peeling construction. It is accomplished in anotherembodiment with an everting double sleeve which is pulled distally, but,by virtue of the eversion of the sleeve, does not slide over the rolledstent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the vasculature of the brain showing atypical placement of an intra-cranial stent.

FIG. 2 is schematic diagram of the vascular of the brain illustratingthe circle of Willis and arteries supplying the circle of Willis.

FIG. 3 is an elevational view of the rolled stent mounted on aninsertion catheter.

FIG. 4 is a cross section of a preferred embodiment of the stentcatheter.

FIG. 5 is a cross section of a second preferred embodiment of the stentcatheter.

FIG. 6 is a cross section of a third preferred embodiment of the stentcatheter.

FIG. 7 is a view of a simple embodiment of the stent.

FIG. 8 is a view of a preferred embodiment of the stent.

FIG. 9 is a view of a preferred embodiment of the stent.

FIG. 10 is a view of a preferred embodiment of the stent.

FIG. 11 is a view of a preferred embodiment of the stent.

FIG. 12 is a view of an alternative embodiment of the stent.

FIG. 12 a is a view of a preferred embodiment of the stent.

FIG. 13 is a view of an alternative embodiment of the stent.

FIG. 13 a is a view of an alternative embodiment of the stent.

FIG. 14 is a view of an alternative embodiment of the stent.

FIG. 15 is a view of an alternative embodiment of the stent with slatsrunning in the longitudinal direction.

FIG. 16 is a cross section of diseased artery with the stent in place.

FIG. 17 is a sectional view of a diseased artery with the stent beingused in conjunction with aneurysm clips.

FIG. 18 is a sectional view of a diseased artery with the stent beingused in conjunction with detachable coils.

FIG. 19 is a view of an embodiment of the stent in place within adiseased artery.

FIG. 20 is a view of an embodiment of the stent in place within adiseased artery.

FIG. 21 shows and alternative embodiment of the stent.

FIG. 22 is a view of an embodiment of the stent in place within adiseased artery.

FIG. 23 shows an alternative embodiment of the stent.

FIG. 24 shows an alternative embodiment of the stent in place within adiseased artery.

FIG. 25 shows a view of a tear away sheath for use in retaining anddeploying a rolled sheet stent.

FIGS. 26 and 27 show a cross section of the tear away sheath assembly.

FIG. 28 shows a view of a peeling sheath mechanism for use in retainingand deploying a rolled sheet stent.

FIG. 29 shows a second view of a peeling sheath mechanism for use inretaining and deploying a rolled sheet stent.

FIG. 30 is a cross section of a peeling sheath mechanism for use inretaining and deploying a rolled sheet stent.

FIG. 31 shows a view of a zip-strip mechanism for use in retaining anddeploying a rolled sheet stent.

FIG. 32 shows a second view of a zip-strip mechanism for use inretaining and deploying a rolled sheet stent.

FIG. 33 shows an alternative embodiment of the zip-strip mechanism usinga number of zip-strips.

FIG. 34 shows an alternative embodiment of the zip-strip mechanism foruse in retaining and deploying a rolled stent.

FIG. 35 shows an alternative embodiment of the zip-strip mechanism foruse in retaining and deploying a rolled stent.

FIG. 36 shows an adherent bead mechanism for use in retaining anddeploying a rolled stent.

FIG. 37 shows an adhesive strip mechanism for use in retaining anddeploying a rolled stent.

FIG. 38 is a cross section of the everting delivery mechanism.

FIG. 39 is a cross section of the everting delivery mechanism with theretaining sleeve partially everted.

FIG. 40 shows a stent delivery mechanism for delivering several stentswith the same delivery catheter.

FIG. 41 shows a stent delivery mechanism for delivering several stentswith the same everting delivery catheter.

FIG. 42 shows a view of a tabbed stent which facilitates loading ordelivery.

FIG. 43 shows a view of a tabbed stent loading or delivery mechanism.

FIG. 44 shows a view of a tabbed stent loading or delivery mechanism.

FIG. 45 shows a view of a tabbed stent loading or delivery mechanism.

FIG. 46 shows a cross section of a proximal hub assembly for use withthe various catheters.

FIG. 47 shows a cross section of a proximal hub assembly for use withthe various catheters.

FIG. 48 shows a cross section of a proximal hub assembly for use withthe various catheters

FIG. 49 shows another embodiment of a liner translator which uses a handheld electric motor.

FIG. 50 shows a cross section of a proximal hub assembly for use withthe various catheters

FIG. 51 shows a cross section of a proximal hub assembly for use withthe various catheters.

FIG. 52 shows a cross section of a gun assembly for use with the variouscatheters.

FIG. 53 shows a cross section of a gun assembly for use with the variouscatheters.

FIG. 54 shows a cross section of an in-line gun assembly for use withthe various catheters

FIG. 55 shows a heat release mechanism for a self expanding stent.

FIG. 56 shows a heat release mechanism for a self expanding stent.

FIG. 57 shows a heat release mechanism for a self expanding stent.

DETAILED DESCRIPTION OF THE INVENTIONS

FIGS. 1 and 2 show the vasculature of the brain in sufficient detail tounderstand the invention. The brain 3 is supplied with blood through thecarotid and the vertebral arteries on each side of the neck. Theimportant arteries include the common carotid artery 4 in the neck,which will be the most common access pathway for the stent, the internalcarotid 5 which supplies the opthalmic artery 6. The external carotid 7supplies the maxillary artery 8, the middle meningeal artery 9, and thesuperficial temporal arteries 10 (frontal) and 11 (parietal). Thevertebral artery 12 supplies the basilar artery 13 and the cerebralarteries including the posterior cerebral artery 14 and the circle ofWillis indicated generally at 15. The siphon 12 a of the vertebralartery appears in the intra-cranial vasculature on the vertebralapproach to the Circle of Willis. Also supplied by the internal carotidartery are the anterior cerebral artery 16 and the middle cerebralartery 17, as well as the circle of Willis, including the posteriorcommunicating artery 18 and the anterior communicating artery 19. Thesiphon 5 a of the internal carotid artery 5 appears in the intra-cranialvasculature on the carotid approach into the Circle of Willis. Thesearteries typically have an internal diameter of about 1 mm to 5 mm, mostcommonly from 2-4 mm. The methods and devices described herein allowaccess to these arteries and placement of a stent in these arteries. InFIG. 1, the insertion catheter 2 and stent 1 are shown threaded throughthe common carotid artery 4 and the internal carotid artery 5, with thestent extending into the anterior cerebral artery 16.

FIG. 2 shows the same blood vessels in a schematic view that betterillustrates the Circle of Willis and the arteries which supply thisimportant anatomic feature. The Circle of Willis 15 is a ring ofarteries connecting the internal carotid arteries and the basilar artery(and hence the left and right vertebral arteries) to the anteriorcerebral arteries 16, middle cerebral arteries 17 and posterior cerebralarteries 14. The system provides a redundant supply of blood to thecerebral arteries. The carotid siphon 5 a, which forms an integral partof the internal carotid artery 5, is more clearly visible in this view.Aneurysms, fistulas, AVM's and tumors occurring inside the brain, in theintracranial portion of the carotid arteries, vertebral arteries (andthe portions of those arteries distal to the siphons) and basilarartery, in the circle of Willis or even deeper within the brain may betreated with the stents and delivery systems described below. FIG. 2shows an exemplary use in which a delivery catheter 2 is insertedthrough the aorta into the common carotid, internal carotid, the carotidsiphon and through the Circle of Willis 15 into the middle cerebralartery 17 to treat an aneurysm 65 with a stent which is held on orwithin the distal tip of the delivery catheter.

FIG. 3 shows the overall structure of the stent 1, when mounted in thedelivery catheter 2. The stent 1 is comprised of a single sheet 20 ofElgiloy™, stainless steel, nitinol, plastic or other suitable material.The metals are processed so as to provide a high level of springproperty in the deployed configuration. Such processing includes coldrolling and suitable heat treatment. The stent is rolled tightly aroundthe insertion catheter distal tip 21. Retaining clip 22 holds the sheetin a tight roll around the catheter. The retaining clip or tab isoperated by pull wire 23 which extends out the proximal end of thecatheter. The retaining tab is slidably disposed within the arcuate sidelumen 24 and extends distally from the side lumen to hold the stent in atight roll on the distal tip of the catheter. The retaining clip or tab22 is operably connected to the proximal end of the catheter via apullwire so that the retaining tab may be pulled proximally into thearcuate side lumen to release the stent. The clip mechanism provides fora lower profile than the construction of other stents such as theWinston stent and the Lane stent which require spools or sheaths. Theclip mechanism may be additionally secure to the stent by folding theedge 39 of the stent over the tab so that the tab is positive engaged ina fold of stent material along the edge of the stent. In anotherembodiment, an electrolytic charge may be used to release a securingattachment to the stent, thus allowing for stent expansion and/orrelease from the catheter. The clip may be made of tantalum or otherradiopaque material so that it is clearly visible under fluoroscopy. Theouter diameter of the stent, when rolled tightly around the distal tipof the catheter, will typically be 1-3 French (0.3 mm to 1 mm), and maybe as small as 1 French, about 0.3 mm (0.012 inches or 12 mil), or evensmaller. The stent may also be coated with radio-dense material (tin,tantalum, etc.) to enhance visibility under fluoroscopy. Also,radiopaque markers of tantalum, platinum or gold may be attached to thestent.

FIG. 4 shows the cross section of the insertion catheter 2 with thestent 1 mounted and retained by the retaining clip 22. The retainingclip has a circumferential radius matching the outer diameter of therolled stent, and may be pulled by pullwire 23 into the arcuate sidelumen of the insertion catheter. Upon pull-back of the retaining clip,the stent will release and unroll or unwind to a diameter of about 1 mmor less, or as much as 5 or 6 mm. After release, the stent will have atleast one layer in the unwound state. A single layer may partially coverthe interior surface of the blood vessel wall (see FIGS. 19 and 20), maycompletely cover the surface with a single layer of stent material, ormay cover the interior surface with more than one layer of stentmaterial. Use of multiple layers provides extra columnar and radialstrength (i.e., resistance to compression or resistance to unwinding orre-rolling in response to compressive forces) vis-à-vis a single layer,and this extra strength is beneficial in view of the modifications ofthe stent as described below to enhance the radial and longitudinalflexibility of the stent. Another embodiment allows for a single layerstent across the vessel anomaly to be occluded and one or more layers atthe stent vessel anastomosis site (the endpoints of the stent).

FIG. 5 shows a cross section of the stent 1 mounted in an insertioncatheter sheath 25. The stent is tightly rolled within the distal tip ofthe catheter sheath and it is delivered to the target site within thedistal tip of the delivery sheath. A push rod 26 with an optionalcentral lumen 27 and a distal face 28 abuts the proximal end of therolled stent. In order to insert the stent within the blood vessel, thepush rod 26 is used to hold the stent in place while the catheter sheathis retracted proximally to uncover the stent, or it is used to push thestent out from the sheath. Once the stent is free of the cathetersheath, it will unroll until it meets the inner wall of the bloodvessel. FIG. 6 shows a cross section of a delivery catheter whichprovides both distal and proximal release mechanisms. The stent 1 istrapped between the push rod 26 and the distal retainer 29. Thereceiving bore 30 of the retainer 29 closely matches the outer diameterof the rolled stent. The internal diameter of the catheter sheath 25also closely matches the outer diameter of the rolled stent. Theexternal diameter of the delivery catheter is only slightly larger thanthe outer diameter of the tightly rolled stent. The stent is rolledtightly and trapped within the bore of the distal retainer. The distalretainer is controlled by control rod 31 which extends the length of thecatheter and passes through the central lumen of the push rod 26.Preferably, the retainer control rod has an outer diameter significantlysmaller than the inside diameter of the tightly rolled stent, so that itdoes not interfere with flexing of the stent during deployment. Theretainer control rod may instead have an outer diameter equal to theinner diameter of the rolled stent, so that the stent is directly rolledaround the control rod and the control rod functions as a spool or coreto support the rolled stent. This delivery catheter is operated byreleasing either the proximal or distal end of the stent throughappropriate movement of the distal retainer, the push rod, or thecatheter sheath. The stent may be released distal end first by pushingthe retainer control rod in the distal direction to release the stent,or it may be released proximal end first by pushing the pushing rodforward and distally out from the catheter sheath or withdrawing thecatheter sheath in the proximal direction to release the proximal end ofthe stent. The need for proximal-end-first or distal-end-first releasewill be determined during surgery, and will be accomplished as medicallyindicated.

The push rod 26 must fit within the catheter sheath with very closetolerances to ensure that the rolled stent is uniformly pushed from thecatheter sheath and the outer roll of the stent cannot get caughtbetween the push rod and the catheter sheath. Thus, the distal tip 32 ofthe push rod is enlarged relative to the proximal portion 33 of the pushrod so that the distal face of the push rod has a diameter which closelymatches the inner diameter of the catheter sheath. The distal face 28 ofthe push rod is provided with a beveled rim 34 around the outercircumference the distal face to force the stent to preferentially sliptoward the center of the distal face and away from possibly interferingpositions between the push rod and the catheter sheath. A beveled rim 35may be applied also to the inside bore of the push rod (FIG. 6) toprevent the inner roll of the stent from slipping into the push rodcenter lumen and getting caught between the push rod and the distalretainer control rod. FIGS. 4, 5 and 6 thus illustrate means of securingthe stent to the distal end of a catheter and retaining the stent in thetightly rolled configuration during insertion, and two means ofinserting the stent into the blood vessel. Other means for retaining thestent include rings, pull-strings, string wraps, bars, a cathetersleeve, and electrolytic fusible joint or fusible link.

The stent may be a simple rolled sheet of Elgiloy™, nitinol, stainlesssteel or other resilient material. Elgiloy™ is preferred because it isless likely for the inner layer of the tightly rolled stent to take aset or become creased or crimped, which may occur in a stainless steelroll when the inner layer of the stent is tightly rolled in itsdeployment configuration. Plastics, bioabsorbable materials, and othermaterials may also be beneficially used. Polyesters, polypropylene,polyethylene, polylactic acid and polyglycolic acid are contemplatedalternative materials for the stent.

The basic embodiment comprises a sheet of Elgiloy™ about 0.0025 to 0.025mm thick (0.1 mils to 1 mil, or 0.0001 to 0.0010 inches). Referring toFIG. 7, the wrap length represented by transverse edge 36 will be about6-75 mm, allowing the stent to expand to diameters from about 1 mm toabout 6 mm with approximately two to three layers after expansion. Thebridge length represented by axial edge 37 (or the longitudinal edge)will vary according to the width of the aneurysm which must be isolatedwith the stent, and may vary from 2 to 20 mm, for example. The stent istempered or formed so that it resiliently unrolls and expands to adiameter of approximately 1 mm to 6 mm, and provides a slight compliancemismatch with the intra-cranial arteries which have internal diametersof about 1 mm to 6 mm. When expanded, the stent intended for mostintracranial applications will comprise a tube of one to three rolledlayers. The stents described above can provide expansion ratios of fiveto one or greater. Expansion ratios of less than five to one may beachieved if desired. For particular intracranial applications, stentshaving more than three layers may be used. Stents comprising less than asingle layer when unrolled will also be useful, as illustrated below inreference to FIG. 18.

The stent will be more flexible, and easier to bend around the varioustwists and turns of the blood vessels, if modified according to FIGS. 8through 12. The stent may have a thickness which gradually increasesalong the transverse edge, as shown in FIG. 8. When the stent isexpanded, the material of the inner layers is thinner than the outerlayers. Thus, the inner edge 38 is thinner than the outer edge 39. Thisconstruction permits the stent to flex sideways even when rolled tightlyto the distal tip of the insertion catheter and mitigates the tendencyof the innermost edge of the stent to be permanently deformed in itsrolled down state. The inner edge may be as small as 0.0025 mm (0.1mil), and the thickness can gradually thicken to 0.05 mm (2 mils) at theouter edge. In FIG. 14, the stent is modified with the provision of ribs40 that extend transversely across the width of the rolled sheet, or ata slight angle to the transverse edge. The wall thickness in theinterstitial portions between the ribs may be quite thin, less than0.0025 mm (0.1 mil), and yet the stent has sufficient resilience toexpand into its open configuration and exert pressure against the innerwall of a small blood vessel. This property will allow the stent toremain in position and maximize the sealing characteristics of thedevice. The ribs may be applied only at the distal and proximal ends ofthe stent, and may be integrally formed as gradually increasing stentthickness.

FIG. 9 shows the stent 1 modified by excision of numerous cutaways 41,42 and 43 leaving slats or ribs 44, 45, and 46 in eventual outer layer47, middle layer 48 and inner layer 49. The segments of slats areseparated by spines or backbones 50. The slats of each segment areoffset so that, when expanded to a roll of approximately three layers,the three layers will overlap to form a barrier between the blood vesselwall and the inner lumen of the expanded stent. The slats shown in FIG.9 are disposed laterally, aligned in the transverse direction across thewidth of the stent sheet, parallel to the distal transverse edge 51 orthe proximal transverse edge. Of course, where the distal and proximaledges are not straight edges (such a construction may assist attachmentto the blood vessel), the slats and cutaways can be described asparallel to the transverse axis of the stent sheet. The stent may bemade with at least one, but preferably two layers instead of the threelayers used for illustrative purposes herein, or four layers or more,and the number of layers will dictate the spacing of the slats and thecutaways. The slatted construction provides longitudinal flexibility byremoving part of the material from the wall of the stent.

As shown in FIG. 10, the slats may be disposed at an angle from thetransverse direction and still create a barrier between the blood vessellumen and the outer surface of the stent. In the outer layer section 47of the stent, the slats are disposed at an angle, shown at angle ofabout 45° from the transverse direction. The angle of 45° is shown asone of the preferred embodiments but is to be considered merelyillustrative of the infinite number of possible arrangements. In themiddle layer section 48 of the stent the slats are disposed at anopposing angle, again shown merely for illustration to be about 45° fromthe transverse direction, but opposite the angle of the slats in theouter layer section. These two layers, when overlapping, will provide anearly imperforate roll, with passages through the wall of the stentonly at the intersections of the cutaways. These passages are, however,blocked by the transversely oriented slats of inner layer section 49.The slats are sized and dimensioned to ensure that, when expanded withinthe target vessel, the three layers together form a barrier between theoutside of the stent and the inside of the stent. Thus if perfect threelayer overlap and alignment were expected, each slat could be of equalsize and the transverse inner layer slats 46 could be the same width asthe passage created by the intersection of the cut-away slots in theother layers. However, to allow for an imperforate wall when the layersare not perfectly aligned and perfectly overlapping in three layers, theinner layer slats 46 are made slightly wider than the correspondingcutaways on the outer and middle layers. The dashed line 52 shown inFIG. 10 illustrates that the center point of cutaway 41 a and 42 b willintersect when the stent is rolled in three layers, and that slat 46 awill correspond to the intersection and block the gap created by theintersection of the two diagonal slots.

FIG. 11 shows that numerous patterns of cutaways may be conceived toprovide a multi-layered stent wherein each layer contains plurality ofslots or perforations, but, when rolled so that the layers are disposedin concentric arrangement, the layers combine to form an imperforatewall. In the outer layer section, the slots are aligned on an angle fromthe transverse axis, while the slots in the middle layer are arranged atan opposing angle relative to the slots on the outer layer. The numerousslots on the inner layer are arranged so as to correspond to the areasof overlap of the outer and middle layer, leaving the slats to cover theopen areas where the slots of the middle and outer layers overlap. Thus,FIG. 11 illustrates that the number and arrangement of slots may behighly variable while still providing an imperforate overallconstruction with highly perforate walls.

FIG. 12 is provided as an illustration of the concept. It is moreclearly demonstrated in the simple embodiment of FIG. 12 that thecutaways 53 a, 53 b and 53 c on the outer layer and the cutaways 54 a,54 b and 54 c will, when the outer layer is rolled over the middlelayer, intersect along lines 55 a, 55 b and 55 c. The slats 56 a, 56 band 56 c on the inner layer are intersected by lines 55 a, 55 b and 55c, and correspond to the expected gap created by the intersection of thediagonal cutaways. The inner section slats may be made larger than theexpected gap created by the diagonals to ensure blockage of the gap whenthe roll is either looser or tighter than exactly three layers, ormisaligned. The concept may be applied to any number of layers, thegeneral rule being that the slats of each layer, when rolled over top ofeach other, form an imperforate wall. Thus, the longitudinal flexibilityof the tightly rolled stent is promoted by ribbed or slattedconstruction (or, alternatively, slotted construction) in which thevarious layers of the stent are provided with numerous slats whichcounter align when the stent is expanded to form an imperforate wallfrom a plurality of perforate layers.

The backbones 50 created between the slatted sections can be arranged sothat they are aligned when the stent is tightly rolled, to provideincreased flexibility during insertion. The backbones may also becreated so that they are aligned when the stent is unrolled and deployedwithin the blood vessel to provide extra flexibility when unrolled inthe install configuration. Careful selection of the tightly rolled sizewill permit alignment of the backbones during both the tight rolledinsertion configuration and the loosely rolled deployed configuration.For example, if the diseased vessel for which the stent is intended isabout 2 mm in inner diameter, it will have an inner circumference ofabout 6.3 mm (2 mm ×π). A stent designed for this size vessel may haveone or more segments with backbones spaced about 6.3 mm apart, so thatwhen unrolled each segment will cover one entire circumference, and thebackbones will all be on one side of the vessel. When rolled tightly tofit within the sheath or upon the distal tip of the catheter (as shownin FIGS. 4 and 5), the stent may be rolled to a diameter of 1 mm or 0.5mm (or, for example, in relation to the preferred embodiments, anyinteger fraction ½, ⅓, ¼ . . . of the deployed diameter, and realizingthat other relationships will apply to other embodiments), so that thebackbones are layered upon each other. Thus all the backbones aredisposed on one side of the roll in both the deployed diameter and thetightly wound diameter. This advantageous feature may be applied tostents having overlapping slats, and thus in the expanded configurationthey will have open slots between the slats, interrupted by theoverlapping backbones. Such and embodiment is illustrated in FIG. 12 a,which shows the stent 1 having groups of slats 56 in the sections 47,48, 49 interposed between backbones 50. The slats are not aligned tocause interfering blocking as shown in FIGS. 10-12, but the sections andbackbones are sized and dimensioned so that the backbones line up witheach other in the tightly rolled configuration to provide increasedflexibility to the stent during insertion.

FIG. 13 shows another embodiment of the ribbed stent. In thisembodiment, a single backbone 50 supports several ribs 57 which areunrestrained at the outer edges of the ribs. The ribs are flat and wide,with gaps 58 on one side of the backbone which are offset from the gapson the other side of the backbone. When rolled into a tight roll (upon acatheter distal tip or inside a sheath, as illustrated in FIGS. 4 and5), or unrolled within a blood vessel, the ribs overlap each other andform an imperforate wall. The ribs on one side of the backbone arealigned with the interstitial gaps on the other side of the backbone,thus creating an interfering pattern in much the same manner asdescribed above in relation to FIG. 9. The backbone is the only regionof this stent that is continuous from the distal end of the stent to theproximal end of the stent, and this eliminates much of the resistance tolongitudinal flexibility and allows the stent to be bent around tightcurves in the vasculature without crimping or creasing.

Note that by shifting any segment of slots upward or downward, therolled stent will have a loosely rolled deployed configuration in whichthe walls of the stent are perforated. Thus, in reference to FIGS. 9,10, 11 or 12, the gaps closed by the slats of the third segment asdescribed above may be maintained open by shifting slats upward ordownward slightly so that they no longer block the gap. Construction ofsuch a perforate multi-layered stent will allow flexibility of the stentin the undeployed and deployed configuration, provide for perforationsallowing vessel ingrowth, better retention of the stent, or ability topass blood into perforating vessels, yet still provide for the extraresistance to compression afforded by multiple layers.

The slots provided in the wall of the stent may be locally enlarged tocreate regions of highly perforate wall in the stent. This may bemedically indicated when it is desired to maintain patency of thenumerous side branches and perforator blood vessels which are suppliedwith blood by the typical intra-cranial blood vessel. In reference toFIG. 13, the circumferentially extending ribs on either side of thebackbone 50 may be aligned so that the ribs on one side overlap the ribson the other side, thereby creating openings in the wall of the deployedrolled stent which correspond to the open areas 58 between the ribs 57.This configuration in shown in FIG. 13 a. The stents of FIGS. 9 through12 may be modified accordingly, providing regions of relatively largerslots which prevent occlusive overlap of the slats, thereby maintainingpatency of many side branches and perforating blood vessels fed by thestented blood vessel. This may be achieved with broad backbones andnarrow slats of minimal width relative to the slots, so that occlusionis achieved only along the overlapping backbones. It may also beachieved by providing some of the slatted areas of a stent constructedaccording to FIG. 11 with overlapping and occluding dimensions whileproviding other slatted areas with dimensions which result in a highlyperforate, non-overlapping or completely patent structure in the looselyrolled deployed configuration.

Another embodiment of the rolled stent is shown in FIG. 15. This stentis a variation of the slatted stent illustrated above. The slats arealigned longitudinally in relation to the catheter and blood vessel, andperpendicular to the transverse edge or wrap length 36. The slots 41,42, and 43 are narrow relative to the slats 59, 60, 61 and 62. To createa loosely rolled stent in a substantially imperforate wall from thisstent, the wrap length 36 is several times longer than the circumferenceof the target blood vessel. When the stent is loosely rolled toapproximate the inner diameter of the blood vessel lumen, the gapsbetween longitudinally oriented slats in one layer will be blocked bythe slats in other layers. Occlusion of the stent wall will occur forall vessel circumferences which are approximately equal to the distancebetween the center of one slat and the center of one slot. Thus animperforate wall is formed from this highly perforate embodiment of therolled sheet stent for vessels with diameters corresponding to lengthsC₁, C₂, and C₃, equivalent to the distance from the reference slat 59 tothe center of each of the various slots. The bar-bell shape of the slots(cutaway portions) creates fusiform or tapered shaped slats joined tothe end bands 63 provides additional flexibility for the stent whentightly rolled to fit within (or upon) the distal tip of the deliverycatheter.

In relation to each of the embodiments described above, the stent may beconfigured to provide a section (either an arcuate segment or alongitudinal segment, which is substantially imperforate, while theremaining portions of the stent are substantially perforate or open.This allows for occlusion of the aneurysm or target site of diseasewhile permitting flow of blood between the vessel wall and the bloodvessel lumen in other areas of the stent. This allows blood flow to anybranch blood vessels or perforator blood vessels which supply blood tothe brain. The “H” shaped stent of FIG. 21 accomplishes this, andvariations on the alignment of the slot patterns on the multi-layeredstents of FIGS. 8 through 12 will accomplish such an arrangement.

All of the stent configurations are intended for use while visualizedunder fluoroscopy. Fluoroscopy will also be used to view the stentduring follow-up to ensure continued proper placement. Thus the stentmay be coated with radiopaque material such as tantalum to enhancevisibility under fluoroscopy. The stent may be coated with a number ofsubstances which help prevent thrombus or coagulation of blood aroundthe stent or in the nearby blood vessel which may be affected by thestent. Paralyne, polyurethane, polyester, polyphosphazene, Dacron,Nylon, silicone, polymers and biopolymers, heparin and albumin coatings,negative ion coatings, tin, and acids such as polylactic acid andpolyglycolic acid may be used. Various medications may be bound to thecoating, and medications such as heparin, methotrexate, forskolin arecontemplated for use. The surface of the stent may also be mademicroporous with perforations of, for example, about 0.001″ diameter toenhance the vessel ingrowth into the stent for better stent/vesselattachment and to improve thrombogenicity.

The stent is placed with the insertion catheter into an artery withinthe skull or brain, such as the many arteries pointed out in referenceto FIG. 1. The catheter is inserted into a blood vessel of a patient,typically the femoral artery, and the distal tip with the stent mountedthereon is steered into an intra-cranial blood vessel of the patient. Inthe close-up view of FIG. 16, the stent is shown in an artery exhibitingan aneurysm which could rupture or lead eventually to occlusion, bothlife threatening events. The blood vessel 64 includes a saccularaneurysm 65. The aneurysm and aneurysm neck may vary in size. Smallaneurysms are those of 0-10 mm diameter. Large aneurysms are 10-25 mm indiameter, and giant aneurysms are greater than 25 mm in diameter.Distance a represents the size of the aneurysm neck. In clinicaldiscussion, a wide-neck aneurysm has a neck which exceeds 4 or 5 mm. Thestents described herein may be used with aneurysms of all sizes.

The placement of the stent 1 straddles the aneurysm. Once in thediseased portion of the intra-cranial artery, the stent is maneuveredinto place in the proximity of the aneurysm, with the stent straddlingor bridging the neck 66 of the aneurysm. Once in position, the retainingclip is pulled back into the side lumen thereby releasing the stentwithin the intra-cranial artery. The solid walled stent, or the modifiedstent, unrolls to form an imperforate barrier between the arterial walland the center of the stent, and immediately isolates the sac 65 fromthe blood vessel lumen 67. This is shown in FIG. 17, in which the stenthas unrolled from an original tightly rolled configuration shown in FIG.16 to a partially unrolled configuration with three layers of stentmaterial.

Upon placement of the stent, the blood flow is redirected from thetarget opening and the aneurysm is isolated from the high blood pressureof the vascular system, and the threat of hemorrhage is eliminated. Inthis manner, a patient showing signs of acute distress from a cerebralaneurysm may be treated immediately in a manner that stops or preventsrupture and hemorrhage. Placement of the stent immediately seals off theaneurysm to protect against bleeding or rupture, in contrast to priorart open walled stent placements used in larger peripheral arterieswhich require significant time for the formation of fibrous tissuewithin the aneurysm and formation of endothelial cells to create abarrier which isolates the aneurysm from the high pressure of thevascular system. Gradual retraction of the aneurysm or tumor afterexclusion and resultant lack of blood flow should relieve any masseffect caused by the size and pressure of the aneurysm or tumor againstother structures in the brain.

The stent may be left in place as the permanent treatment for theaneurysm or target vessel, or it may be used as a temporary means ofre-directing blood flow for stabilizing a patient while considering oractually performing more invasive treatment. Aneurysm clipping, which isone of the standard treatments for intra-cranial aneurysm, is plagued bythe risk of rupturing the aneurismal sac during the surgery. As shown inFIG. 17, the aneurysm may be clipped in accordance with known procedureswhile the stent is in place. To place the clips, the brain must beexposed and dissected away from the aneurysm so that the clips may beplaced at the base of the aneurysm. Rupture during surgery makes thesurgery more difficult, decreases visibility and requires additionaldissection, contaminates the brain with blood, and makes it moredifficult to seal the aneurysm with the clips. With the stent 1 expandedwithin the blood vessel, the brain is dissected away from the aneurysmto expose the outside 68 of the aneurysm. Clips 69 (shown in FIG. 17)may be placed at the neck of the aneurysm and squeezed closed upon theaneurysm, thereby further sealing the aneurysm sac from the bloodvessel. After the aneurysm has been successfully clipped and therebyisolated from the high pressure of the blood vessel, the stent mayoptionally be removed from the lumen of the blood vessel. FIG. 18 showsthat the stent may also be used to immediately isolate the aneurysmafter placement of GDC's. Several Guglielmi detachable coils or othersuch detachable coils 70 are shown inside the aneurysm sac 65. The coilswill, in the usual case, eventually cause coagulation and clottingwithin the aneurysm. However, the patient is at risk during the periodrequired for successful development of the occluding mass caused by thebody's reaction of the coils. To ensure immediate isolation of theaneurysm from the blood vessel, and to ensure that the coils do notescape the aneurysm sac and float downstream to cause embolization orclotting in healthy portions of the blood vessel, the rolled stent isdeployed immediately before or after placement of the coils. When usedin this manner, the stent is used as an adjunctive to surgery to make itsafer and eliminate the complications arising from invasive surgery. Incases where a patient is presented in an emergency condition, perhapssuffering from a ruptured intracranial aneurysm, immediate placement ofa solid walled or slightly perforate stent may be the only way to savethe patient's life while preparing for other surgery. Placement of coilsmay be accomplished through the wall of the stent, where the stent isslightly perforate (with a high metal to vessel wall ratio) or where thecoils may be pushed into the aneurysm through slots in the wall of animperforate stent constructed according to FIGS. 9-16.

FIG. 19 illustrates another embodiment of the stent as well as anothermethod of using the stent to isolate an aneurysm 65 from the bloodstream. The stent 1 has been inserted into the blood vessel 64 andcovers the opening of aneurismal sac 65. A blood vessel 71 (it may be abranch that is supplied by blood vessel 64 or it may supply blood vessel50) joins blood vessel 64 near the aneurysm. A rolled stent whichunrolls to cover all 360° of the blood vessel inner wall will cover boththe aneurysm and the blood vessel 71, but it is usually desirable tomaintain flow to or from this blood vessel. In this case, a stent 1 witha short wrap length is used. The stent has a wrap length which isshorter than the internal circumference of the blood vessel, so thatwhen unrolled within the blood vessel it expands to meet the inner wallof the blood vessel but covers less that the entire circumference of theblood vessel wall. The elasticity and spring force of the stent willhold it in position against the blood vessel wall and isolate theaneurysm from the blood vessel. FIG. 20 illustrates another situationwhere the resilient half stent is used. The blood vessel and branchblood vessel are normal and healthy. Another branch vessel 72 suppliesblood from the main blood vessel 64 to a diseased area 73. The diseasedarea may be an aneurysm or fistula in the branch blood vessel, a tumorsupplied by the branch blood vessel, or any other vascular disease. Thehalf stent has been released within the main blood vessel 64 so that itblocks blood flow to the branch blood vessel, thereby isolating thediseased area from the blood stream. The diseased area will necrose andbe absorbed by the body over time, thereby alleviating the conditionwithout surgery directly in the area of the disease.

When used in this manner in a perfectly round blood vessel, the stentmust have a wrap length of at least half the inner circumference of theblood vessel so that it covers at least 180° of the inner wall of theblood vessel. However, in a real blood vessel which is not perfectlyround, it may be sufficient that the wrap length be about half the innercircumference of the blood vessel, and cover about 180° of the innerwall, and coverage of at least 180° will be useful in a wide range ofblood vessels. In use, it will be most practical to select a wrap lengthwhich results in about 210° to 270° of coverage (with wrap lengthcorresponding to about ¾ of the expected inner wall circumference), toensure a good fit, adequate resilience for expansion and holding power,and sufficient clearance for the branch blood vessel.

The half layer stent shown in FIGS. 19 and 20 may be provided as asingle imperforate sheet, or it may include any pattern of slots asillustrated in FIGS. 6-9. The half layer stent should be mounted on thecatheter distal tip (FIG. 4) or within the catheter sheath (FIG. 5) sothat it is properly aligned with the side branch or aneurysm to beblocked. The retaining clip made of tantalum (or other radiopaquematerial) or a tantalum marker on the sheath will provide the referencepoint for the surgeon during placement, so that rotational andlongitudinal alignment with these markers will allow proper release andplacement of the stent. The rolled stent may be centered under theretaining clip so that the clip corresponding to the side of the vesselwhere the stent is to be placed.

FIG. 22 shows another variation of the stent. This stent is shaped likethe letter “I” or the letter “H.” The backbone 50 is augmented withintegrally formed ribs or tabs 74 extending transversely from thebackbone at the distal and proximal ends of the stents. The transverselyextending tabs create open areas 75. The transverse edge preferablyexceeds the circumference of the blood vessel in which the stent isinserted. The single backbone will provide the occluding surface area ofthe stent, while the ribs serve to provide radial expansive strength forthe stent to provide stronger deployment and holding resilience.

As shown in FIG. 22, the loosely rolled deployed configuration of thestent has the backbone 50 occluding the target vessel 72, while the ribsor tabs extend circumferentially over the entire circumference of theblood vessel to hold the stent in place. The ribs may overlap somewhat,as shown, creating an arcuate open space 75 in what would otherwise bethe wall of the stent. Branch blood vessel 71 is not occluded becausethe stent is placed so that the cutaway portions of the stent overliethe opening into the blood vessel 64. Thus, in use, the stent providedwith an occluding sheet with transversely extending retaining bands onthe distal and proximal ends is placed within the blood vessel so thatthe occluding sheet occludes a diseased branch vessel, aneurysm or otherAVM while circumferential portions of the blood vessel opposing theoccluding diseased branch vessel, aneurysm or other AVM are not coveredby the occluding sheet, thereby allowing blood flow between the bloodvessel and any branch blood vessel communicating with the blood vesselat a site opposite the occluding sheet.

FIGS. 23 and 24 illustrate another embodiment of the rolled sheet stent.This stent takes the shape of an open frame with an open central area76. Side-frame pieces 77 a and 77 b will provide the occluding surfacefor this stent, and distal end and proximal end pieces 78 will provideradial support for the stent. When rolled within a blood vessel as shownin FIG. 24, the overlapping side frame pieces occlude the diseasedbranch vessel, aneurysm or other AVM designated generally at item 73. Aswith the stent of FIG. 21, this stent is placed within the blood vesselso that the open portion overlies the healthy branch vessel 71 while theoccluding sheet made up in this instance of side frame pieces covers thediseased blood vessel 72. In FIG. 24, several perforator vessels 79 areshown to illustrate that there will typically be several perforatorsleft open and unoccluded by the open area of the stent, while otherperforators, such as perforator 80, may be occluded by the stent. In thedeployed configuration, the stents of FIGS. 22 and 24 will appear to bevery similar, comprising an arcuate occluded segments and an arcuateunoccluded segments. The occluded segment is created by the spine 50 inFIG. 22 or side pieces 77 a and 77 b in FIG. 24, and the unoccludedsegment is created by the central opening 75 or 76.

The stents described above are very flexible, and exhibit a highlyindependent longitudinal structure (that is, the ends of the stent arevery independent, and constraint of one end will not cause restraint ofthe other). The delivery systems described below are useful fordeploying these stents within the body while minimizing the need toforce the components to slide past the stent material. One embodiment ofa non-sliding stent deployment mechanism is illustrated in FIG. 25. FIG.25 shows a rolled sheet stent 1 mounted on the tip of an insertioncatheter 2 and restrained by a thin tear-away sheath 81. Starter notches82 are cut in the tear-away sheath to ensure that tearing is easilyinitiated. Cords 83 are looped over the entire length of the tear awaysheath, and are initially set in the starter notches. The loops 84extend from the proximal end of the tear-away sheath to the distal endof the sheath, and the cord is then routed into the central lumen 85 ofthe insertion catheter 2 through side ports 86. The cord may be securedto a pullwire 87 residing within the insertion catheter and operablefrom the proximal end of the catheter. The insertion catheter may be amicrocatheter having a lumen or it may be a guide catheter or guide-wiresuch as a hollow cross wound guide catheter.

FIG. 26 shows this construction in cross section, where the multiplelayers of the rolled stent are shown constrained by the tear-away sheath81, and the cords 83 are visible within the cross section of thecatheter. The underlying cord segment 90 (the segment that runs underthe sheath) may be tied to the overlying cord segment 91, in which casethe entire loop will move over the stent and operate to tear the sheath81. Instead, the underlying cord segment can be secured to distal end ofthe sheath or the inner lumen of the insertion catheter, and not to theoverlying cord segment. In this case, only the overlying segment willmove distally upon pullback of the pullwire while the underlying segmentwill not move relative to the stent, except as it is lifted and pulledaway from the stent as the loop rolls forward in response to thepullback. FIG. 27 shows an alternative construction of the tear-awaydevice where the zip cords are routed into a guide sheath 92 which maybe used with the delivery catheter. Note that in both FIGS. 26 and 27,the sheath is provided with a proximal extension 93 which can serve tosecure the stent to the insertion catheter 2. The loops and pull cordperforate through the sheath where necessary for attachment to thepullwire.

In FIG. 27, the tearing progresses from the distal end of the tear-awaysheath to the proximal end of the tear away sheath, in contrast with theconstruction of FIG. 26, in which pulling the zip cord in the proximaldirection results in distal movement of the loops because the cord isdirected out the distal end of the catheter before being engaged in thetear-away sheath. In these embodiments, the tear away sheath is made of0.0001 to 0.001 in plastic tube such as heat shrinkable PET. The loopsand cords may be made from any suitable cord, line, wire or suturematerial. The stent 1 may be any of the stents describe herein, or otherprior art stents. The insertion catheter 2 may be a small diametercatheter tube or a guide-wire which is steerable within the vasculature.Where the insertion catheter is comprised of a guide wire, the guidewire with the stent mounted on the distal tip may be steered to thetarget site without the aid of an addition guide-wire.

FIG. 28 shows a non-sliding deployment mechanism for the rolled sheetstent. This mechanism operates like a banana peel. The tear-away sheath81 in this embodiment surrounds the stent 1 and holds it in a tight rollat the distal tip of the catheter 2. The catheter may or may not includea distal core or spool for support of the stent. Where a distal core isused, it may be comprised of the distal portion of a guide-wire whichallows the entire assembly to be steered into the target site. Thesheath is scored with one or more perforation lines 94, and preferablyhas two such perforations lines located 180° apart on the sheath. A pulltab 95 is integrally formed with the sheath 81, and connects to thesheath at or near the distal edge of the sheath and extends to theproximal end of the catheter, or it may connect to a pullwire near thedistal tip of the catheter 2, so long as it is operably connected to apulling control mechanism on the proximal end of the catheter. Thesheath 81 is removed from the stent by pulling the pull-tabs in theproximal direction. As shown in FIG. 29, when the pull-tabs 95 arepulled proximally, the sheath tears along the perforation lines 94 andthe sheath 81 is peeled away from the stent like a banana peel. Thecross section shown in FIG. 30 illustrates that the sheath 81 foldsbackward over itself, and peeling section 96 moves relative to thestent, while the unpeeled proximal 97 section of the sheath need notmove relative to the stent and the stent need not move relative to thecatheter 2. As more clearly shown in FIG. 30, two pull tabs are providedand arranged circumferentially about the sheath, and any number of pulltabs may be provided. The amount of sliding between the sheath and thestent is minimized in this embodiment. When completely unpeeled, thesheath 81 may be withdrawn with the catheter 2.

FIG. 31 shows a non-sliding deployment mechanism for the rolled stent.As in the previous figures, the sheath 81 surrounds the stent 1 andholds it in a tight roll at the distal tip of the catheter 2. Thecatheter may or may not include a distal core or spool for support ofthe stent. The sheath 81 is provided with a zip-strip 100 which isconnected to the pull-strip 101 which may be integrally formed with thezip strip 100. The pull-strips are connected to a proximal pullingmechanism. The zip-strip, pull strip and sheath are constructed in amanner similar to zip-strips used commonly for cellophane wrapping oncigarette packages, CD cases, express mail envelops, etc. FIG. 32illustrates the zip-strip mechanism of FIG. 31 after the zip-strip hasbeen partially pulled back. The sheath 81 is torn along the zip strip asthe pull-strip is pulled away from the stent. The stent is graduallyuncovered as the tear progresses along the sheath, and there is no needto cause the stent to slide past the sheath. The sheath may be pulledinto the delivery catheter or it maybe left in place between the stentand the blood vessel.

The zip-strip mechanism can be modified as shown in FIG. 33, where anumber of zip-strips 100 are placed under the sheath 81 so thatsubstantially the entire circumference of the sheath overlies azip-strip. Each zip-strip 100, shown in phantom because they lieunderneath the sheath 81, is a separate strip secured by adhesive, heatseal or otherwise, to the overlying sheath 81. When all the pull-strips101 are pulled proximally, the sheath is torn into shreds correspondingto the underlying sip-strips. The embodiment facilitates removal of theentire circumference of the sheath after release of the stent. Dependingon the surrounding vasculature, the stent may release before all stripsare pulled completely off the stent. When these strips are caughtbetween the stent and the blood vessel wall, they may be removed bycontinued pulling on the strips. Due the number of strips, any sheathremaining between the stent and the blood vessel wall may be removed ina peeling or everting action, rather than sliding over the outer layerof the stent. The plurality of zip-strips may also be comprised of asingle sheath which is scored or perforated to form a plurality ofzip-strips weakly connected or unconnected along the perforations.

FIG. 34 shows an alternative construction for the zip-strip. Whereas inFIG. 31 a cord is placed under the sheath, and tension on the cordresults in tearing of the sheath, in FIG. 34 the cord is made integrallywith the sheath, and is constructed by scoring lines on the sheath toform the strip 102. Starting notches may be used in place of full lengthscoring lines. The pull cord 101 is tied to the strip at extending tab103. As with the other embodiments, proximal tension on the pull stripacts to tear the strip 102 away from the sheath, thereby releasing thestent.

FIGS. 35, 36, and 37 show embodiments of the rolled stent in which thesheath is replaced with an edge binding in which the outer edge of thestent is glued, taped, soldered, or welded to the underlying stentlayer. FIG. 35 shows an example of such an embodiment. The outer edge ofthe rolled stent 1 is sealed to the outer surface of the outer layer 104which lies underneath the edge 39. The stent thus forms a sealed roll ofstent material. The zip-strip 100 is placed under the outer wrap of thestent and attached to the pull strip 101. The stent material ispre-scored as shown by the dotted lines to facilitate tearing. When thezip-strip is pulled proximally, the outer wrap is torn neatly along thescored line, and the stent unrolls. In this embodiment, there is nosheath remaining, and only the pull-strip and zip-strip are left forremoval through the catheter. The tape may be formed of pre-formedpolyester tape, or may be formed by painting a strip of silicone,co-polymers, UV curable polyurethanes, for example, which may be appliedin liquid or flowable form and removed in a cohesive strip.

FIG. 36 shows a similar self expanding stent secured to the distal tipof catheter 2. A joining bead 105 joins the outer edge 39 of the stent 1to the underlying layer, similar to the bead shown in FIG. 34. Thezip-strip 100 is placed under the bead, so that the zip-strip will tearthe bead when pulled, thereby releasing the stent. A bead of polyesterwill adhere sufficiently to the stent to provide retention, and willyield readily to the tearing force of the zip-strip. FIG. 37 shows yetanother variation of the edge binding release, wherein an adhesive strip106 is used to tape the edge of the stent down to the underlying layer.The tape is secured to pull cord 101, which is operated from theproximal end of the catheter to pull the tape away from the stent.

FIG. 38 shows yet another non-sliding everting deployment mechanism forthe rolled sheet stent. The stent is rolled tightly within an evertingsheath comprised of a very thin plastic sleeve 109, and may be rolledabout the catheter 2, which in this embodiment may be a guide-wire usedto place the stent at the target site. The sleeve 109 is not secured tothe stent except by virtue of the tight fit. The sleeve is secured tothe distal end of the sheath 110, and may have in inward wrap 111 at itsproximal end to isolate the catheter core 112 from the stent and preventthe thin walls of the stent from slipping into any clearance between thecatheter core and the sheath. The catheter core 112 keeps the stent frommoving proximally within the sheath. The stent is released when thesheath 110 is pulled back from the stent (as indicated by the arrow inFIG. 39) thereby pulling the sleeve over and off of the stent. Thesleeve 109 is everted (turned inside out) as the catheter sheath ispulled back. When pull-back is complete, the stent will be released andthe sleeve will be inside out.

Each of the release mechanisms described above may be used to deploymultiple stents from the same delivery catheter. This may be desirablein cases where several aneurysms or AVM's are encountered in closeproximity to each other. FIG. 40 shows a delivery system similar to thatshown in FIGS. 25 through 27. Several stents 1 a, 1 b, and 1 c are shownmounted on delivery catheter 2, which also includes a support core 113.The stents are retained in the tightly rolled condition by the tear-awaysheaths 81 a, 81 b and 81 c. The cord 83 is shown looped over thesheath, and run under the sheaths 81 a, 81 b and 81 c. A second cord maybe placed on the opposite side of the catheter. The cord is routed intothe lumen of the delivery catheter through port 114, and extend to theproximal end of the catheter where it is connected to pullingmechanisms. As illustrated, a pair of cords may be used to tear eachsegment of sheath from each stent. One pair of cords may operate to teara single long sheath which covers all three stents away from each stent,or a separate pair of cords and a separate length of sheath may beprovided for each stent. The operation of this stent delivery mechanismis similar to the operation of the single stent delivery mechanism, withthe cords being pulled proximally in this case, to tear the sheathsalong pre-weakened tear lines. The sheaths may be secured to the corewith bands 115 to facilitate their removal after expansion of stents. Insimilar fashion, the everting sheath delivery catheter of FIG. 38 may beloaded with more than one stent. This embodiment is shown in FIG. 41,where several stents 1 a, 1 b, and 1 c are shown mounted on evertingdelivery catheter 2. As the everting sheath 109 is withdrawn, the stentsare released one at a time. The zip-strip delivery catheter of FIG. 31,and the peel-away delivery catheter of FIG. 28, may also be constructedto hold and deliver a plurality of stents disposed within the sheath atthe distal tip of the catheter.

Loading the stents onto the distal tip of the catheter is facilitated bythe construction and method illustrated in FIGS. 42 and 43. The rolledsheet stent 20 which makes up the stent 1 is provided with a pair ofears or tabs 116, one on the distal edge of the stent and one on theproximal end of the stent. Each tab is provided with thread hole 117through which a retaining cord may be threaded. The pull cord 101 isthreaded through the thread holes and secured to the delivery catheter2, as shown in FIG. 43. As shown in FIG. 44, the cord is used to holdthe stent in place while the sheath 81 is applied. The stent is coveredwith an appropriate sheath, which may be any sheath disclosed herein orin the prior art. The sheath may be applied by heat shrinking a materialsuch as PET over the stent. Other retaining structures may be applied,such as the adhesive bead or strip shown in FIG. 36 or 37 (tape). Theears or tabs may be snipped off the body of the stent after the sheathhas been put in place over the stent, as illustrated in FIG. 45. Thecord may remain in place to be used as the tear away cord. While theholes are placed in the tabs to best facilitate rolling of the stent onthe catheter, the holes shown in the tabs may be moved into the mainbody of the stent, and penetrate through all layers of the stent. Itshould be recognized that the intermediate embodiments shown in FIGS. 43and 44 may be used as a final embodiment, wherein the retaining cord isused as a pull cord. The tabs may be left in place or snipped away insuch an embodiment. The pull cord may be secured with any releasablemechanism, such as a detente, a breakable joint or electrolytic joint. Asingle pull cord may be used, threaded through both thread holes, or aseparate pull cord may be used for each tab. Just as tabs 116 facilitatetie down of the outer edge of the stent, tabs may be added to the insideedge 38 to facilitate initial placement of he stent inside edge upon theinsertion catheter 2.

Each of the stent release mechanisms illustrated above require aproximal hub assembly which includes controls for pulling or pushing thevarious pull cords or push rods. The hubs may be referred to generallyas linear translators, as they translate various turning, twisting,squeezing, and other motions into linear motion of the pull cords orpush rods. The hub assembly is preferably hand held and easily operatedto impart appropriate pulling or pushing forces on a longitudinal membersuch as the pull cords, push rods, or the catheter sheath. Thumb slideassemblies commonly used in pull-wire steerable catheters may be used,but the frictional forces between the sheath and the pull cords can bevariable and surprisingly high. The proximal hub assemblies disclosedbelow are designed to provide smooth longitudinal pulling or pushingforce, and, where possible, to allow one-handed operation. FIG. 46 showsa proximal assembly designed to provide the longitudinal movement neededin the various stent retaining devices. The hub 118 includes a barrel119 with a central bore 120 which houses the various portions of thecatheter. The delivery catheter proximal end 121 includes the guidecatheter or guide sheath 92, the delivery catheter 2 disposed within theguide catheter, and the zip cords or pull-wire 87 are disposed withinthe delivery catheter. A sliding traveler 122 is slidably mounted withinthe bore 120 of the hub. A thumb-screw 123 is mounted in the exterior ofthe hub, and has internal threads which ride on the external screwthreads 124 provided on the hub. The traveler 122 includes a finger 125which extends through longitudinal channel 126 into an annular groove onthe inner surface of the thumbscrew 123 so that rotation of thethumbscrew and movement of the thumbscrew along the exterior of the hubcauses the traveler to move with the thumbscrew. The traveler is securedto the pullwire 87 so that any movement of the traveler pushes or pullsthe pullwire. When used in combination with the tear-away sheathillustrated in FIG. 25, for example, the rotation of the thumb screw istranslated into gentle, smooth, controllable and even tension on thepullwire and loops 84, and clean tearing of the tear-away sheath alongthe line established by the starter notches 82 shown in FIG. 25. The hubassembly may be combined with any of the embodiments disclosed herein,or with any pull-wire structure disclosed in the prior art. It should benoted that reversal of the direction of turning of the thumb-screw willresult in a distal movement of the traveler, so that the assembly may beused to push a push rod or wire.

The hub assembly 118 shown in FIG. 46 is assembled so as to connect thethumbscrew 123 to the pullwire 87, so that the pullwire may be pulledproximally. The traveler may be connected to the insertion catheter 2,as shown in FIG. 47, so that the thumbscrew operates on the insertioncatheter. Note in FIG. 47 that the insertion catheter 2 extendsproximally, and it is in contact with the traveler 122 and secured tothe traveler. Thus the delivery catheter 2 may be advanced distally orwithdrawn proximally by action of the thumbscrew. An additional traveler127 and thumbscrew 128 are added to the hub assembly, engaging thepullwire 87 at a location proximal to the point of engagement of theoverlying guide sheath. Three or more overlying sheaths may likewise beindependently operated with travelers in similar manner.

FIG. 48 shows an alternative mechanism for pulling the stent sheathcords. The thumb roller 130 is connected to the finger via a small axle131 (and a duplicate thumb-roller is on the opposite side of the axle),and the finger 125 is in turn connected to the traveler 122. The gearedcircumference 132 of the thumb roller tightly engages the rollingsurface 133, either by providing a tight high friction fit or via a rackand pinion assembly with a geared surface on the surface of the thumbroller. The traveler 122 is connected to the longitudinally movingcatheter component, whether it be the pull cords, everting sheath,zip-strips or other component. With this construction, the operator ofthe catheter may provide smooth pulling or pushing force on thelongitudinal sliding member, and the friction lock provided by the tightfit will hold the component in place relative to other members ofcatheter assembly.

FIG. 49 shows another embodiment of a linear translator which uses ahand held electric motor. The translating rod 136 is threaded, andengages the threaded bore of traveler 137. The traveler is held withinthe hub in slidable but non-rotating manner by the runner 138, whichmoves in longitudinal channel 126 so that rotation of the translatingrod forces longitudinal translation of the traveler. The translating rodis attached to electric motor 139 which may be operated in eitherdirection to rotate the threaded translating rod and cause pulling orpushing force on the traveler. Movement of the traveler 137 causescorresponding movement of the pull wire 87 or push rod. The motor 139may be a cordless motor having forward, reverse and lock positions, andmay actually be comprised of a cordless screw driver or similarcommercially available motor drive, with the translating rod having ahexagonal cross section to mate with the screw driver chuck. The motorhandle is integral with the motor body, thus comprising an in-line motordrive. With this embodiment, the gross positioning of the distal tip ofthe catheter and the final deployment of the stent may be accomplishedwith one hand. Because the motor body is in-line with the catheter, itmay be conveniently used as a handle for gross adjustment and fineadjustment of the catheter. Additional motor and translating screwassemblies may be coupled to the catheter sheath, or to both thecatheter sheath and the pull wire, to permit motorized fine adjustmentof these components. Foot switches may be used to operate one or more ofthe motors so that the operator's hands are free to manipulate thecatheter.

The linear translating mechanism shown in FIGS. 50 and 51 operate byapplying hydraulic force to an actuator disposed within the distal endof the delivery catheter 2. This eliminates the need for a pullwire orother structure that must extend the entire length of the catheter,enabling construction of a more flexible catheter. As shown in FIGS. 50and 51, the proximal hub assembly comprises a hydraulic actuator 140including a chamber 141, a piston assembly including an input ram 142and a hydraulic disk 143 connected to the handle 144 via the ram. Theram is threaded, and engages the threaded bore of the hydraulic chamber.Turning the handle drives the ram and disk into the chamber, and forceshydraulic fluid (most conveniently, saline solution) through thecatheter lumen 145 and into distal hydraulic actuator 146. Distalhydraulic actuator has its own disk 147 and ram 148, which are forced tomove as the distal hydraulic chamber 149 is filled with fluid. Thedistal ram may be the pull cord, strips, or wires used to tear thevarious embodiments of the stent retaining mechanism, or it may be smallrod attached to the cords, strips or wires. The ram 148 slides throughsealed opening in the distal chamber 149. The distal hydraulic chamber146 may be reversed in orientation and placed proximally of the stent,as shown in FIG. 51, so that the pulling force may be applied from theproximal side. Also shown in FIG. 51 is the use of the syringe 150 whichserves as the hydraulic chamber. The syringe plunger 142 is connected tothe handle 144 through linkage 151. It can readily be appreciated thatthe fluid supply and orientation of the distal actuator may be varied tocause pushing or pulling according to design preferences.

FIG. 52 shows an embodiment of a caulk gun-type linear translator, whichcomprises a gun assembly 154 including a frame 155, a grip 156, atrigger 157 mounted on a pivot 158, a reversing arm 159 mounted on asecond pivot 160, friction engagement block 161 which engagestranslating rod 162, and a return spring 163 which acts to push theengagement block in the position shown. In FIG. 52, the pull cord isattached to the translating rod 162. Squeezing the trigger 157 causesthe hammer 164 at the top of the trigger to push the bottom of thereversing arm forward, and thus the top of the reversing arm pushes thefriction engagement block 161 rearward. The friction engagement blocktilts slightly as it moves rearward, and engages the translating rod 162with frictional force, and carries the translating rod with it. Thisrearward movement of the translating rod results in a pulling force onthe pull wire and the tear strips, zip-strip, or pull cords attached toit. Reversal of the action, to create a pushing action, may beaccomplished by removal of the reversing arm, in which case the triggerwill act directly on the engagement block. FIG. 53 includes many of thesame parts as the gun of FIG. 52. The frictional engagement block isreplaced by pinch mechanism 165. The pinch mechanism is a compressiblefrustoconical tube 166, and is surrounded by conical pusher 167 mountedon the top of the trigger 157 and opposed by return spring 163. As theconical pusher is forced rearward by the trigger action, it compressesthe compressible tube, and causes the tube to grip the translating rod162, so that the translating rod 162 is carried rearward with thecompressible tube. After the stroke, the compressible tube is forced toits original position by the return spring.

In FIG. 54, the gun drive mechanisms of FIGS. 52 and 53 are modified bymoving the grip and trigger to an in-line position, meaning that thelength of the trigger 157 is generally parallel to the long axis of thecatheter itself. This allows the gun handle 156 to be used as a handlefor the catheter itself, and permits easier operation of the trigger157. The gun assembly is modified to permit in-line operation,principally by addition of the extension 168 which operably connects thetrigger to the reversing arm 159. The reversing arm is modified byaddition of a contact block 169 sized and dimensioned to obstruct thedownward movement of the trigger extension 138.

FIGS. 55, 56 and 57 illustrate another embodiment of non-sliding releasemechanisms for the self expanding stents. In each of these embodiments,the retaining structure is separated by melting under the heat of anichrome wire. In FIG. 55, the self expanding stent is secured to thedistal tip of catheter 2. A joining bead 171 joins the outer edge 39 ofthe stent 1 to the underlying layer, similar to the bead shown in FIG.34. The bead is preferably made with an adherent or adhesive materialwith a low melting temperature, such as polyester. The heating wire(preferably nichrome) 172 is placed under the bead, and grounded throughground wire 173. When a small and safe current is passed through thenichrome wire, it heats up and melts the bead, thereby releasing thestent. FIG. 56 shows a similar construction, with the outer edge 39 ofthe stent 1 glued to the underlying layer with several plugs of adherentmaterial placed in holes 174. Again, the plugs are made of with anadherent or adhesive material with a low melting temperature, such aspolyester, so that passage of current through the heating wire melts theplugs, thereby releasing the stents. The plugs may extend throughmultiple layers or all layers of the stent, thus locking them togetherand serving as meltable locking pins, or they may extend only throughthe upper layer and serve an adhesive dabs to secure the outer layer tothe underlying layer. In FIG. 57, the stent 1 is secured with the sheath81, as illustrated in various embodiments above, and the heating wire172 runs under the sheath, attached to the ground wire 173. Passage ofelectric current through the heating wire causes it to heat upsufficiently to melt the sheath in the vicinity of the wire, therebymelting a tear in the sheath and releasing the stent. In reference toFIGS. 55, 56 and 57, the sealing material used in each embodiment may becomprised of electrolytically dissolvable material and the electricalconnections may be used to pass current through the material to causethe electrolytic dissolution of the material. Electrolytic materialsuseful in these embodiment include, for example stainless, bismuth,lead, etc. The area of desired electrolytic dissolution can becontrolled by coating the stent with a polymer or biopolymer (PET, forexample, perhaps impregnated with therapeutic agents) in all areas inwhich dissolution of the stent is not desired.

The overall structure of the stent insertion catheter has been describedin various embodiments. Any structure commonly used in the prior art toinsert devices into the blood vessels may be used, and any system may beused. There is some variation on the method of deployment ofintraluminal devices, and all such variations may be employed incombination with the inventions described above. Basic access to thevasculature is expected to be accomplished percutaneously, using theSeldinger technique. This requires use of an insertion needle, followedby an insertion guide which is placed over the insertion needle,followed by a large insertion catheter which is inserted over theinsertion guide. The insertion catheter extends only a few centimetersinto the blood system, and serves to protect the insertion point fromunnecessary damage from the several catheters which may be inserted inthe course of a single operation. A guide catheter, discussed above inrelation to the various embodiments, may then be inserted through thevasculature to a point near the diseases portion of the blood vessel.Placement of the guide catheter may be accomplished with the aid of aguide wire. With this guide catheter in place, the delivery catheter ofthe various embodiments may be inserted and steered to the diseasedsite. Thus it is desirable to use an insertion catheter that issteerable, and can be snaked, pushed and twisted through theintracranial vasculature. For many of the embodiments discussed above,the insertion catheter may be made of an 0.020 in guidewire, or evensmaller guidewires as they become available. Hollow guidewires canprovide the supporting structure as well as the central lumen used forthe pull wires used in the various embodiments, and have already provencapable of safe insertion into the vasculature. For the many embodimentsdescribed above which use sheaths, various sheaths are commerciallyavailable.

This specification has described several means for retaining, deliveringand deploying stents inside the vasculature of the human brain. Theinventions described above have been developed in the environment ofintra-cranial stent placement. However, the benefits provided by thevarious embodiments may be employed in any environment, includingintraluminal placement of a variety of implants, or operation of avariety of devices from remote locations. Although emphasis has beenplaced on description of the stent deployment mechanisms in combinationwith rolled sheet stents, these stent deployment mechanisms can be usedto deliver and deploy any manner of stent. A large number of variationsin implementation of the inventions may be expected. Catheter placementmay be facilitated with the use of common guide catheters and guidewires. Expansion of the stent may be aided by a micro-balloon placed atthe tip of the insertion catheter. Other features described, such as thematerials of the stent, the arrangement, number and degree of openingsor slats, and geometry of the release tab may be improved upon asexperience with the devices and methods described above dictates. Thevarious hub mechanisms and release mechanisms may be mixed and matchedaccording to design preference. Thus, while the preferred embodiments ofthe devices and methods have been described, they are merelyillustrative of the principles of the invention. Other embodiments andconfigurations may be devised without departing from the spirit of theinventions and the scope of the appended claims.

1. A stent delivery system comprising: an insertion catheter having adistal end and a proximal end; a rolled stent mounted on the distal endof the insertion catheter, said rolled stent having a small diameterconfiguration and a large diameter configuration; said rolled stenthaving an outer edge overlapping an outer surface of an outer layer;binding means for affixing the outer edge to the outer surface of theouter layer of said rolled stent, wherein the binding means forms asealed roll of the rolled stent when the rolled stent is in its smalldiameter configuration; and a release mechanism comprising a zip-stripplaced under the outer layer of the rolled stent and a pull-strip, saidzip-strip attached to the pull-strip.
 2. The stent delivery system ofclaim 1 wherein said outer layer is pre-scored to facilitate tearing,wherein said zip-strip when pulled proximally tears the rolled stentalong pre-scored lines.